The letters "S" and "T" with a cedilla "Ş" should turn to ones with a comma "Ș" in Romanian.
ŞȘ
Supported in: Roboto, Barriecito, DM Serif, Montserrat.
Letters with acute accents should get the "kreska", which "is steeper than usual and originates from the optical center of the base letter."
ćńú
Supported in: Barriecito, Fira Sans, Playfair, Bahianita.
All tested fonts automatically convert the glyph based on adjacent characters without taking locale into account.
ßẞ
Straße
STRAßE
Supported in: Work Sans, Asap, Vollkorn, Cormorant.
When surrounded by uppercase letters, "i" should not turn to "I" but to "İ" instead. No tested languages support that, even with TR locale.
Iİi
Diyarbakır
DiYARBAKIR
Not supported!
When "í" (iacute) is followed by "j", the "j" should turn to jacute.
míjn
mí jn
Supported in: Montserrat, Playfair, Muli, Nunito, Work Sans, Bahianita, Cabin, Anton, Varela, Pacifico, Merriweather.
When two "l" are separated by a "·" (periodcentered), the space between those characters should be reduced.
l·l l ·
paral·lel
Supported in: DM Serif, Literata, Oswald, Slabo, Nunito, Rubik, Fira Sans, Libre.